As a video signal processing speed has increased, a method of encoding/decoding ultra high definition (UHD) video has been studied. A method of processing UHD video as well as HD video without any problems even when UHD video is received using an existing HD receiver has been studied.
A UHDTV needs to provide a screen having an improved frame rate, bit depth, color sampling format, etc. as compared to an existing HDTV, in order to provide a high-quality image. Among the others, when a bit depth increases from 8 bits to 10 bits, a luma value corresponding to Y of YcbCr composing one pixel value is changed from a value of 0 to 255 to a value of 0 to 1023, thereby increasing an express range and providing a higher-quality image. For a color gamut, two methods, that is, non-constant and constant luminance color encoding methods may be provided. In order to use the constant luminance color encoding method using wide color gamut, a bit depth needs to be extended to 10 bits.
However, since an existing HD receiver supporting an 8-bit bit depth cannot display video with a 10-bit bit depth, there is a need for a method of supporting a 10-bit bit depth while being compatible with an 8-bit bit depth, but a solution thereto has not been provided. In addition, there is a need for a method of signaling video data having different bit depths but a solution thereto has not been provided.